The Ford’s Theatre Mystery (a mystery adventure full-length chapter books for kids) #670057

Three kids, Lillian, Walter, and William are in the Ford's Theatre. The two boys accompanied Lillian to run an errand at the theater. While waiting for their turn, William got bored and decided to roam around the theater. Minutes later, Walter decided to find William. 
When the three kids are about to leave the theatre, William relays a funny incident about a man suspiciously digging up at the back of the Ford’s Theater. Lillian tells the two boys about the legend she heard from the caretaker of the theater. Walter instantly suspects a correlation between Lillian and William’s story. And just like that, the three kids went on a mission to find out if their suspicion is true. Will the kids confirm the old legend about Lincoln’s buried possessions? If so, will they be able to locate it before somebody else does?